Blowout preventer with variable inside diameter

ABSTRACT

A variable inside diameter blowout preventer capable of sealing off a bore or around an object against high well pressures, and which may be either a ram-type preventer or an annular preventer, and wherein a plurality of anti-extrusion members are disposed for radial movement on a curved plate, either semi-cylindrical or annular, and so that the adjacent members fully overlap each other from the plate radially inwardly, and each of the anitextrusion members is movable independently to limit or prevent extrusion of a resilient sealing member therewith regardless of the external configuration of the pipe, kelly or other object being sealed off by the sealing member.

United States Patent [1 1 LeRouax 1 BLOWOUT PREVENTER WITH VARIABLE INSIDE DIAMETER [75] Inventor: Robert K. LeRouax, Houston, Tex.

[73] Assignee: I-IydrilCompany,Houston,Tex.

[ Notice: The portion of the term of this patent subsequent to July 29, 1992, has been disclaimed.

[22] Filed: Nov. 5, I973 [21] Appl. No.: 412,770

Related U.S. Application Data Continuation-impart of Ser. No. 325.530, January 22,

1973, abandoned.

1 1 *Oct. 28, I975 Primary ExaminerMartin P. Schwadron Assistant Examiner-Richard Gerard Attorney, Agent, or FirmPravel & Wilson [5 7] ABSTRACT A variable inside diameter blowout preventer capable of sealing off a bore or around an object against high well pressures, and which may be either a ram-type preventer or an annular preventer, and wherein a plurality of anti-extrusion members are disposed for radial movement on a curved plate, either semicylindrical or annular, and so that the adjacent members fully overlap each other from the plate radially inwardly, and each of the anit-extrusion members is movable independently to limit or prevent extrusion of a resilient sealing member therewith regardless of the external configuration of the pipe, kelly or other object being sealed off by the sealing member.

12 Claims, 11 Drawing Figures US. Patent Oct.28, 1975 Sheet 1 of6 3,915,425

US. Patent Oct. 28, 1975 Sheet 2 of6 3,915,425

U.S. Patent 0a. 28, 1975 Sheet 3 of6 3,915,425

U.S. Patent 0m. 28, 1975 Sheet 5 0% 3,915,425

US. Patent Oct. 28, 1975 Sheet 6 of6 3,915,425

BLOWOUT PREVENTER WITH VARIABLE INSIDE DIAMETER CROSS-REFERENCE TO RELATED APPLICATION This application is a eontinuation-in-part of US. patent application Ser. No. 325,530 filed Jan. 22, I973 copending herewith, and now abandoned.

BACKGROUND OF THE INVENTION The field of this invention is blowout preventers for oil wells and the like.

Annular blowout preventers made by the Hydril Company, an example of which is shown on page 2742 of the "Composite Catalog for 1970-71, have been in extensive commercial use for a number of years. Such blowout preventers provide a fully-open bore therethrough so that drill bits, reamers, casing hangers and other large diameter tools can freely pass therethrough, but when actuated to the closed position, the packing of each such preventer is forced inwardly to reduce its bore and automatically adjust its size and shape in sea]- ing contact with whatever object happens to then be in the bore of the preventer, thereby closing off the annular space around such object to prevent a blowout of well pressure from below. If no tool is in the well, the bore of the preventer can be fully closed to prevent a blowout.

Although such Hydril blowout preventers are very satisfactory for relatively low well pressures in the range of from about 2,000 p.s.i. to 5,000 p.s.i., it is generally desirable to use a ram type blowout preventer above such pressures, and above 10,000 p.s.i. well pressure, it has heretofore been considered essential to use a ram type blowout preventer of a predetermined opening size because of the inability to satisfactorily prevent extrusion of the rubber of the preventers at such higher pressures.

SUMMARY OF THE INVENTION The present invention relates to blowout preventers wherein a resilient sealing member or members are provided for closing a well bore or sealing with a pipe or other object disposed in the bore and wherein antiextrusion means are mounted with the sealing member or members to prevent extrusion thereof over a relatively large variable range of bore diameters for the preventer, and wherein the blowout preventers of this invention may be of the ram type or the annular type, and are yet capable of sealing off much higher well pressures than with prior known annular blowout preventers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical sectional view of a portion of a blowout preventer of this invention in the form of a ram type preventer;

FIG. 2 is a plan view, partly in section, of an antiextrusion means and the parts therewith for a half portion of the blowout preventer of FIG. I and taken generally on line 2-2 of FIG. 3;

FIG. 3 is a partial elevational view taken on line 33 of FIG. 2, illustrating the ram type blowout preventer of this invention looking from the outside towards the center of a well bore;

FIG. 4 is a partial view taken on line 4-4 of FIG. 3 to illustrate particular details of the anti-extrusion means of this invention;

FIG. 5 is an isometric exploded view of two of the anti-extrusion members used in the blowout preventer of this invention;

FIG. 6 is a sectional view showing one-half of the anti-extrusion means and parts therewith of FIG. 2, and showing in particular the anti-extrusion members in the contacting position with a well pipe for preventing extrusion of the resilient sealing means longitudinally;

FIG. 7 is a view similar to FIG. 6, but showing only the inner portions of the anti-extrusion members in the positions they assume when engaging a square shaped tubular member such as a kelly in a well bore;

FIG. 8 is a cross-sectional view of one rarn taken on line 8-8 of FIG. 1;

FIG. 9 is a cross-sectional view taken on line 9-9 of FIG. 11;

FIG. 10 is a view similar to FIG. 1, but illustrating the blowout preventer of this invention as it would appear in the annular type of preventer;

FIG. 11 is a view similar to FIG. 8, but showing the annular preventer in the closed or sealing position with a well pipe.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, the letter 8 refers generally to the form of the blowout preventer of this invention shown in FIGS. 1-8, which is the ram type of preventer. Briefly, the preventer B includes a housing H which has a central longitudinal bore 10 through which a pipe P or other object is adapted to extend in the known manner for well operations. The housing H is constructed so that it is positioned in a stack of blowout preventers or in a string of well casing or pipe in any suitable manner, as will be well understood by those skilled in the art. The blowout preventer B has a replaceable assembly A (FIG. 2), the details of which will be described hereinafter, which has a central longitudinal bore II which may be opened up to provide a central opening which corresponds in size substantially to the longitudinal bore 10 of the housing H so that the preventer B does not interfere with normal operations through the bore 10 when it is in the opened or retracted position. However, the blowout preventer B may be moved to the closed or sealing position (FIG. 1) so as to seal with a pipe P or other object extending longitudinally in the well bore I0.

In the form of the invention shown in FIGS. 1-8, the blowout preventer B includes a pair of rams R which are preferably identical and which are disposed in the conventional blowout preventer body or housing H. Each of the rams R is suitably connected to a conventional power means generally indicated by the letter M (FIG. 1), which is shown for only the right-hand ram R in FIG. 1. The rams R are adapted to be moved to the closed or contacting position of FIG. I and then further pressure is applied through the power means M for forcing a resilient yieldable sealing means or member S of each ram R into sealing contact with the external surface of the pipe P. By reason of the particular construction of the present invention, extrusion of the yieldable sealing means S of each of the rams R is prevented or inhibited throughout a variable inside diameter range of sealing positions by anti-extrusion members E and F, the details of which will be hereinafter described (FIGS. 2-5).

Although the blowout preventer housing H may be constructed in any manner suitable for receiving each of the rams R, as best seen in FIG. 1, the housing H has a lateral opening or recess 12 for each of the rams R. The ram housing H is preferably made with an upper flange "la and a lower flange b, with suitable bolt holes 10c through each of the flanges for bolting or otherwise connecting the housing H in a stack of blowout preventers or in a string of well casing or pipe in the known manner.

A conventional head or bonnet I4 is connected to each side of the body or housing H (only the right-hand bonnet 14 is illustrated in FIG. 1). Each head or bonnet 14 has a recess 14a (one of which is shown in FIG. I) and each of which is aligned with the lateral openings 12 in the housing H so as to form a continuation thereof. The rams R are received in their respective recesses 140 when they are in the retracted or fully opened position.

A piston rod extends through a suitable seal 14b in an opening Me of each head or bonnet 14. Each piston rod 15 extends to a piston 16 of conventional construction which is a part of the power means M and which is disposed in a cylinder 17 or the like having an end cap or closure 18 therewith in any known manner. For purposes of illustration, a fluid inlet line 18a is shown for introducing air, hydraulic fluid or other operating fluid into the cylinder 17 for moving the piston 16 inwardly towards the center of the bore 10. Another fluid line 14d is provided for introducing air, hydraulic fluid or other fluid into the cylinder 17 for moving the piston 16 outwardly (to the right as viewed in FIG. 1) to retract the particular ram R connected therewith. It will be understood that various systems and apparatus for the power means M may be employed and the invention is not limited to the specific form illustrated in FIG. 1. It should also be understood that a power means M is provided for the left-hand ram R as viewed in FIG. 1, in the same manner as the power means M illustrated for the right-hand ram R in FIG. I.

For ease of description, the details of only one of the rams R will be described hereinafter, at least for the most part, and only when it is necessary to show the inter-action of the two rams while the other ram will be specifically identified. However, it will be understood that the two rams R are preferably made in the same manner.

Thus, each ram R has a ram carrier 20 which is connected to the piston rod or stem 15, preferably in the conventional releasable manner, utilizing a button 150 on the rod 15 fitting into a suitable slot 20b in the ram carrier 20. In the preferred form of the invention, the ram carrier 20 is formed of steel or other relatively rigid material and is preferably substantially semicylindrical in cross-sectional shape (FIG. 8). The ram carrier 20 is provided with an internal recess or surface 20a which is likewise substantially semi-cylindrical in cross-sectional shape and which is adapted to receive a seal element 21, preferably having an external convex surface 210 which substantially conforms with the internal surface 20a (FIG. 8). The seal member 21 is formed of rubber or other yieldable material and it has therewith side anti-extrusion plates 22 formed of steel or other metal which are adapted to engage the inside surface of an inwardly extending lip 120 on the recess 12.

The seal member 21 is confined at its upper end between the ram carrier 20 and an upper ram confining and alignment plate 24 (FIG. I) which plate 24 is secured to the carrier 20 by one or more cap screws 26 or other suitable securing means. It is to be noted that the upper surface 20b of the ram carrier 20 engages and slides relative to the upper surface of the recess 14a and I2. Similarly the upper surface 21b of the seal member 21 engages and seals with the upper surface of the recess 12.

The ram R also has a lower ram confining and alignment plate 25 which preferably extends for the full depth of the ram and which is provided with an alignment shoulder 25a which is engaged by the ram carrier 20 (FIG. 1). Such shoulder 25a or any other suitable engaging means provides for the retraction of the plate 25 outwardly with the carrier 20, but it permits inward movement of the carrier 20 relative to the plate 25 after the inward movement of the plate 25 is stopped by engagement with the opposite plate 25 on the other ram R.

It is to be noted that the vertical or longitudinal area between the upper alignment plate 24 and the lower alignment plate 25, and inwardly of the seal member 21, forms a pocket or recess which is generally semicylindrical in shape for receiving the replaceable assembly A which are normally the primary replaceable parts of the ram R. Such parts may be preassembled and inserted initially into position, as will be more evident hereinafter. Also, replacement assemblies including such parts may be used when necessary.

Such replaceable assembly A of the ram R includes a yieldable resilient sealing element 5 formed of rubber or other similar yieldable material. Upper antiextrusion members E, F are provided above the sealing member S and similar anti-extrusion members E, F are provided as the lower anti-extrusion means below the sealing member S, the details of which will be described hereinafter. The seal member S is distorted from its position shown in FIG. I so as to move radially inwardly into contact with the external surface of the pipe P for sealing engagement therewith when a blowout condition occurs in a well. The member 21 functions with the seal member 5 during such distortion which is caused by the movement of the ram carrier 20 radially inwardly, as will be more evident hereinafter.

The upper anti-extrusion members E, F are identical to the lower anti-extrusion members E, F in the preferred form of the invention, except that they are upsidedown with respect to each other. Therefore, the de tails of the anti-extrusion members E, F will be hereinafter explained and the same parts will be identified and explained briefly with respect to the anti-extrusion members E, F.

The upper anti-extrusion member E form a first set, each of which is preferably identical and which are alternately disposed with respect to a second set of antiextrusion members F. The members E, F are carried in a retainer plate 35 which is generally semi-cylindrical in shape (FIG. 2). The retainer plate 35 preferably has two or more upstanding studs or pins 35a which are adapted to be releasably connected to the plate 24 thereabove (FIGS. 1-3) so that the retainer plate 35 moves with the upper ram confining and alignment plate 24. They both preferably have the same shape and are each formed with a radial end surface such as indicated at 35b for the plate 35. The corresponding end surface 24a (FIG. I) is vertically aligned with the surface 35b of the plate 35 and such surfaces are adapted to contact corresponding surfaces on the opposite ram R when the rams R move to the position shown in FIG. 1.

For receiving the anti-extrusion means E and for guiding same for radial movement relative thereto, the retainer plate 35 has a slot 36 formed for each of the anti-extrusion members E, each of which has substantially parallel vertical sides 36a. Each member E has substantially parallel vertical sides 37 which engage the surfaces or sides 36a of the slot 36 so that the members E are guided radially relative to the retainer plate 35, as will be more evident hereinafter.

Each member E is formed with an upper surface 370 which is disposed slightly below the upper surface of the slot 36. To keep each member E from falling away from the plate 35 in the event the rubber adjacent thereto is torn or otherwise damaged so that the member E is no longer supported by the rubber, a pair of retaining pins 38 are provided which operate in recesses 36b in the sides 36a of the slot 36 and also in slots 37b formed in the side walls 37 of each member E. Preferably, each slot 37b has a rearward opening 37c that communicates with a horizontal opening 39 internally of each member E which receives a locking member 40. Such construction facilitates the assembly of the members E in the plate 35 because the locking member 40 is formed with a recess 40a on each side thereof which accommodates each of the pins 38 so that they do not extend outwardly beyond the outer surfaces of the sides 37 so long as the recesses 40a are aligned with the pins 38. At such point, the locking member 40 is only partially inserted into the horizontal opening 39, and a threaded plug 41 is only partially threaded into an opening 39a which is disposed outwardly of the horizontal flat opening 39. When the pins 38 are aligned with the slots 36b, the locking member 40 is forced to its innermost position (FIG. 2) and the plug 41 is threaded to its fully inserted position of FIG. 2 so that thereafter the pins 38 project outwardly from the surfaces 37 and are thus retained in the slots 36b during relative radial movement of the member E with respect to the plate 35. It is to be noted that the double slots 36b, 37b for each of the pins 38 serves to provide for a stroke of the member E radially a distance equal to substantially the full length of both of such slots 36d and 37b while only one-half of the length of such stroke is required for each of the slots 36b and 37b.

The inner or forward part of each of the antiextrusion members E is formed with an anti-extrusion surface 43 which is normally substantially horizontal and is the upper surface at the inner end of each member E. Such surface 43 coacts with each of the adjacent anti-extrusion members F, as will be more evident hereinafter and as illustrated in FIGS. 5 and 6 of the drawings. For this reason, the upper body of each member E is preferably tapered to form a triangular portion 44 to accommodate converging movements of the members E and F as they move radially inwardly away from the retainer plate 35.

The lower surface 42 (FIGS. 3 and 4) of each member E is bonded or is otherwise secured to the rubber or other material of the sealing member S. The particular shape illustrated for such surface 42 in the drawings improves the adhesion of the surface 42 to the sealing member S, but it will be appreciated that other configurations for such surface 42 may be provided.

Each of the anti-extrusion members F is preferably identical to each other and each is received in a slot 46 of the retainer plate 35. The sides 46a of each slot are preferably substantially parallel and extend vertically for engagement with corresponding surfaces 47 on each of the members F. The upper surface 470 of each member F is adapted to engage the upper surface of each slot 46. Removable retainer pins 48 are similarly mounted to the pins 38 and they provide for similar guidance with respect to the members F. Thus, each member F has side recesses 47b with an opening 47c therethrough (FIG. 5) communicating with an inner recess 49 (FIGS. 2 and 5) in which a locking element 50 having notches 50a is disposed. The pins 48 are inserted into the slots 47b and are initially positioned in the openings 47c so that they do not project beyond the sides 460 until the pins 48 have been moved into alignment with guide recesses 46b, at which time, the locking member 50 is moved forwardly to its position shown in FIG. 2 and the lock screw 51 is threaded into the final position shown in FIG. 2. The pins 48 are thus in a position to move in the slots 47b and 46b in the same manner as the pins 38 move in the slots 36b, 37b, as heretofore explained.

It is to be noted that the inner lower corner of the lower surface 52 of each member F is positioned over and in contact with the surface 43 of the adjacent member E which is urged upwardly by the rubber therebelow to assure such contact. The surface 52 is not bonded to the rubber of the sealing member S (FIG. 4), but the rearward portion 53 of each member F is bonded to the rubber of the sealing member S. Thus, there is a sliding movement between the surfaces 43 and 52 as the members E and F move radially inwardly from their normally retracted position (FIG. 2) to their anti-extrusion inner positions such as illustrated in FIGS. 6 and 7. Each of the members E and F is movable independently of each other so that when the sealing material S is moved into sealing contact with an object having a square shape such as the kelly K (FIG. 7) or some other shape other than the round shape of the pipe P, each of the extrusion members E, F may move independently until it contacts the external surface of such kelly K or other member to provide the maximum possible anti-extrusion with such members E, F.

At each end of the retainer plate 35, it is preferable to provide a half member F-l (one of which is shown in FIG. 2) which is essentially one-half of a member F, but is modified to provide for a guiding and retention thereof on the plate 35 by means of a guide bolt 55 which extends through a slot 56 in the member F-I and into the plate 35.

The lower anti-extrusion members E, F are made substantially identical to the upper anti-extrusion members E, F except that they are reversed as illustrated in FIG. I and they would generally assume the identical positions relative to a pipe P or a kelly K, as should be well understood from the foregoing description.

In the operation or use of the form of the invention shown in FIGS. 1-8, the rams R are normally in the opened or retracted position within the recess [40 for each of the rams R to provide a longitudinal bore II which corresponds substantially to the bore 10 of the housing H. When it is desired to close off the well bore 10 with the blowout preventer B, the rams R moved inwardly towards each other by hydraulic pressure acting on the pistons 16. Such inward movement is continued until the inner radial ends or edges 35b of the retainer plates 35 and the corresponding radial surfaces 24a on the confining plates 24 of the two rams contact each other so that further inward movement of such plates 35 and 24 is prevented. The inner edges 25a of the plates 25 also contact each other at such time. Thereafter, continued movement of the piston 16 inwardly causes a distortion of the sealing members S so that they move radially inwardly and sealingly engage the external surface of the pipe P (FIG. 6) or the kelly K (FIG. 7) or any other object which is in the well bore 10. In some instances, the sealing material S may even seal with contact by the opposite sealing members when there is no object in the well bore.

After the retainer plates 35 have been moved to the innermost position (FIG. I) and during the further inward distortion or movement of the sealing members S into engagement with the pipe P or other object, the anti-extrusion members E, F and E, F move radially inwardly in response to the inward radial movment of the rubber or other resilient material of the sealing members S. Since such anti-extrusion members E, F and E, F are disposed radially and since there is an overlapping of the surfaces 52 and 43 throughout the full circumference or annular space around the pipe P or other object, the metal of such anti-extrusion members forms a continuous metal surface above and below the sealing members S so as to inhibit or prevent longitudinal extrusion of the rubber of the sealing material 8. When the object to be sealed off is the kelly K of FIG. 7 or some other object which does not have a cylindrical outer surface such as a pipe P, the members E and F move independently of each other until they engage the external surface of the kelly K and in such instances, they leave some areas above and below the sealing material S where metal from the anti-extrusion members E, F and E, F' does not fully confine the sealing members S. However, the areas which are thus unconfined are relatively small and under normal pressure conditions the effect of such anti-extrusion members is still sufficient to prevent any substantial extrusion of the sealing material 8.

When it is desired to retract the blowout preventer B from the sealing position to the retracted position, the movement of the pistons 16 outwardly is accomplished by introducing hydraulic pressure through the line 14d and such action moves the rams R outwardly away from each other. The initial relief of the pressure on the rams R from the pistons I6 causes the rubber of the sealing material S to return to its normal undistorted condition of FIG. 1 and the anti-extrusion members E, F and E, F are moved with such sealing material to the retracted position of FIGS. 1 and 2.

In the form of the blowout preventer 8-] shown in FIGS. 91l, the housing H-l is modified as compared to the housing H so as to accommodate the annular form of the blowout preventer 5-1. As illustrated in the drawings, the housing H-l includes a lower housing section 112 having an annular recess 112a for receiving an annular sealing member S-1 and an annular piston 116 formed of rubber or similar material. The recess 112a is further defined by a housing section or cover 114 which is secured to the housing section 112 by bolts 1140 or other suitable securing means. A fluid pressure line IIZb is provided in communication with the recess 112a for the inlet and outlet of fluid pressure with respect to the resilient annular piston 116 to control the opening and closing of the blowout preventer 5-1, as will be more evident hereinafter. An air bleed passage 1141: is also provided for the initial bleeding of air from the annular space around the piston 116. For connecting the housing H-] in a stack of blowout preventers, or to suitable flanges of the well pipe or casing above and below the blowout preventer 8-], connecting threaded studs 1120 and ll4c are preferably provided, although any other suitable connecting means may be employed. The connecting studs 114s are preferably disposed longitudinally in alignment with the connecting studs 112C, although this is not essential.

The blowout preventer B-l preferably includes a replaceable assembly A-l which has the annular resilient yieldable sealing element or member 8-] which corresponds with the sealing members S, except that the sealing member 8-] is completely annular. The sealing member 5-] preferably has a dished out or concave inner surface 133 (FIG. 10), the same as the inner surface of each of the sealing members S (FIG. I), so that when the sealing member is in the sealing position with the pipe P (FIGS. 9 and I] the rubber of the sealing member and the upper and lower anti-extrusion members E, F and E, F are all in engagement with the pipe P, whereby longitudinal extrusion of the sealing member S-1 (or the members S in FIG. 1) is prevented. Upper anti-extrusion means is provided by antiextrusion members E, F which are identical to those heretofore described in connection with the form of the invention shown in FIGS. 1-8. Lower anti-extrusion means is provided by lower anti-extrusion members E, F, which are also identical to the same parts in the blowout preventer B.

In the operation or use of the blowout preventer 8-1, the normal undistorted position of the annular sealing member 5-1 is illustrated in FIG. 10, wherein the full open bore corresponding to the bore of the housing H-l is provided through the sealing member 5-1. When it is desired to seal off around the pipe P or other object in the bore 110, fluid pressure is introduced through the line 112!) so as to compress the resilient piston I16 radially inwardly to move the sealing member S-l radially inwardly and engage same with the external surface of the pipe P or other object within the well bore. The anti-extrusion members E, F and E, F move radially inwardly with the rubber of the sealing material S-l in the same manner as heretofore described with respect to each of the sealing members S and they also engage the external surface of the pipe P as shown in FIGS. 9 and 11 so as to confine the rubber of the sealing member 8-] therebetween and inhibit or prevent longitudinal extrusion thereof due to well pressure or fluid pressure acting in either longitudinal direction thereon.

Upon a release of the pressure within the chamber or recess 1120, the piston 116 returns by its inherent resil iency to the undistorted diameter shown in FIG. 10 and likewise, the sealing member S-l returns to its normal undistorted position of FIG. 10, carrying with it the anti-extrusion members E, F and E, F. It will be understood that the anti-extrusion members E, F are carried in and are supported in the same manner with a retainer plate 135 which corresponds with the plate 35 of FIGS. [-8, but which is annular or cylindrical rather than being semi-cylindrical as the plate 35. A similar plate 135 is also provided inthe same manner for the lower anti-extrusion members E and .F', the detailed construction of which is the same as heretofore described in connection with FIGS. 3-5.

Instead of the dished out or concave surface 133 on the member S-1, or the similar surface on members S, the shape may be modified, or recesses or the like in the members 5-] and S may be provided, the purpose of which is to compensate, or partially compensate, for the smaller volume of the space available for the rubber of the members S and 5-1 when in the sealing position (FRI 11) compared to the volume available for the members S and S4 in the retracted position (FIGS. I and The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention I claim:

1. A blowout preventer adapted to seal with a pipe or other object in a well bore or to close same in the absence of any object in the well bore, comprising:

a resilient sealing member having an inner curved surface adapted to engage a pipe or the like in a well bore;

a rigid retainer plate mounted with the sealing member and having an inner curved surface generally conforming with the inner curved surface of said sealing member;

means for urging said sealing member radially inwardly relative to said inner curved surface of said plate for effecting a seal with a pipe or the like in a well bore or with itself for closing a well bore; and

first anti-extrusion means including plural antiextrusion members mounted with said plate and movable radially relative thereto in response to radial inward movement of said sealing member for contacting portions of the pipe or object in the well bore, or other anthextrusion members in the absence of any object in the well bore. for thereby inhibiting extrusion of the sealing member longitudinally in the area radially inwardly of said plate when fluid pressure acts on said sealing member.

2. The blowout preventer set forth in claim 1, wherein:

said plate is substantially semi-cylindrical and is adapted to be mounted as a part of a blowout preventer ram; and

said sealing member is substantially semi-cylindrical.

3. The blowout preventer set forth in claim 1, wherein:

said plate is annular; and

said sealing member is annular.

4. The blowout preventer set forth in claim 1, including:

second anti-extrusion means including plural antiextrusion members mounted with said plate on the opposite side longitudinally of said sealing member from said first anti-extrusion means and movable radially relative to said plate in response to radial inward movement of said sealing member for contacting portions of the pipe or object in the well bore, or other anti-extrusion members in the ab sence of any object in the well bore, for inhibiting extrusion of the sealing member longitudinally in the area radially inwardly of said plate when fluid pressure acts on said sealing member from either m longitudinal direction.

5. The structure set forth in claim 4, wherein said first 5 and second anti-extrusion means each includes:

a first set of radially disposed anti-extrusion members circumferentially spaced from each other and mounted for radial movement relative to said plate;

a second set of radially disposed anti-extrusion members, each mounted alternately with respect to each of said anti-extrusion members in said first set; and

said anti-extrusion members in said first and second sets having overlapping surfaces, the extent of overlap of which increases as the anti-extrusion members move radially inwardly relative to said plate.

6. The structure set forth in claim 5, wherein:

each of said anti-extrusion members is bonded to said sealing member and is movable therewith independently of each of the other anti-extrusion members whereby said anti-extrusion members may move different, radial distances so as to contact with a kelly or other non-round object when the sealing member seals therewith.

7. The structure set forth in claim I, wherein said first anti-extrusion means includes:

a first set of radially disposed anti-extrusion members circumferentially spaced from each other and mounted for radial movement relative to said plate;

a second set of radially disposed anti-extrusion members, each mounted alternately with respect to each of said anti-extrusion members in said first set; and

said anti-extrusion members in said first and second sets having overlapping surfaces, the extent of overlap of which increases as the anti-extrusion members move radially inwardly relative to said plate.

8. The structure set forth in claim 7, wherein:

each of said anti-extrusion members is bonded to said sealing member and is movable therewith indepen dently of each of the other anti-extrusion members whereby said anti-extrusion members may move different radial distances so as to contact with a kelly or other non-round object when the sealing member seals therewith.

9. The structure set forth in claim 7, wherein:

each of said anti-extrusion members in said first set has substantially parallel sides; and

said plate has a slot for each of said anti-extrusion members in said first set with side walls which are substantially parallel to each other and are engaged by said parallel sides of said anti-extrusion members.

10. The structure set forth in claim 7, wherein: each of said anti-extrusion members in said first and second sets has substantially parallel sides; and said plate has a slot for each of said anti-extrusion members in said first and second sets with side walls which are substantially parallel to each other and are engaged by said parallel sides of said antiextrusion members.

11. The structure set forth in claim 7, including:

retainer means with each of said anti-extrusion mem ber in said first and second sets for retaining same with said plate while permitting relative radial extrusion members to facilitate the assembly and movement thereof. disassembly of said anti-extrusion members with l2. The structure set forth in claim ll, wherein: respect to said plate. said retainer means is releasable from said anti- 

1. A blowout preventer adapted to seal with a pipe or other object in a well bore or to close same in the absence of any object in the well bore, comprising: a resilient sealing member having an inner curved surface adapted to engage a pipe or the like in a well bore; a rigid retainer plate mounted with the sealing member and having an inner curved surface generally conforming with the inner curved surface of said sealing member; means for urging said sealing member radially inwardly relative to said inner curved surface of said plate for effecting a seal with a pipe or the like in a well bore or with itself for closing a well bore; and first anti-extrusion means including plural anti-extrusion members mounted with said plate and movable radially relative thereto in response to radial inward movement of said sealing member for contacting portions of the pipe or object in the well bore, or other anti-extrusion members in the absence of any object in the well bore, for thereby inhibiting extrusion of the sealing member longitudinally in the area radially inwardly of said plate when fluid pressure acts on said sealing member.
 2. The blowout preventer set forth in claim 1, wherein: said plate is substantially semi-cylindrical and is adapted to be mounted as a part of a blowout preventer ram; and said sealing member is substantially semi-cylindrical.
 3. The blowout preventer set forth in claim 1, wherein: said plate is annular; and said sealing member is annular.
 4. The blowoUt preventer set forth in claim 1, including: second anti-extrusion means including plural anti-extrusion members mounted with said plate on the opposite side longitudinally of said sealing member from said first anti-extrusion means and movable radially relative to said plate in response to radial inward movement of said sealing member for contacting portions of the pipe or object in the well bore, or other anti-extrusion members in the absence of any object in the well bore, for inhibiting extrusion of the sealing member longitudinally in the area radially inwardly of said plate when fluid pressure acts on said sealing member from either longitudinal direction.
 5. The structure set forth in claim 4, wherein said first and second anti-extrusion means each includes: a first set of radially disposed anti-extrusion members circumferentially spaced from each other and mounted for radial movement relative to said plate; a second set of radially disposed anti-extrusion members, each mounted alternately with respect to each of said anti-extrusion members in said first set; and said anti-extrusion members in said first and second sets having overlapping surfaces, the extent of overlap of which increases as the anti-extrusion members move radially inwardly relative to said plate.
 6. The structure set forth in claim 5, wherein: each of said anti-extrusion members is bonded to said sealing member and is movable therewith independently of each of the other anti-extrusion members whereby said anti-extrusion members may move different radial distances so as to contact with a kelly or other non-round object when the sealing member seals therewith.
 7. The structure set forth in claim 1, wherein said first anti-extrusion means includes: a first set of radially disposed anti-extrusion members circumferentially spaced from each other and mounted for radial movement relative to said plate; a second set of radially disposed anti-extrusion members, each mounted alternately with respect to each of said anti-extrusion members in said first set; and said anti-extrusion members in said first and second sets having overlapping surfaces, the extent of overlap of which increases as the anti-extrusion members move radially inwardly relative to said plate.
 8. The structure set forth in claim 7, wherein: each of said anti-extrusion members is bonded to said sealing member and is movable therewith independently of each of the other anti-extrusion members whereby said anti-extrusion members may move different radial distances so as to contact with a kelly or other non-round object when the sealing member seals therewith.
 9. The structure set forth in claim 7, wherein: each of said anti-extrusion members in said first set has substantially parallel sides; and said plate has a slot for each of said anti-extrusion members in said first set with side walls which are substantially parallel to each other and are engaged by said parallel sides of said anti-extrusion members.
 10. The structure set forth in claim 7, wherein: each of said anti-extrusion members in said first and second sets has substantially parallel sides; and said plate has a slot for each of said anti-extrusion members in said first and second sets with side walls which are substantially parallel to each other and are engaged by said parallel sides of said anti-extrusion members.
 11. The structure set forth in claim 7, including: retainer means with each of said anti-extrusion member in said first and second sets for retaining same with said plate while permitting relative radial movement thereof.
 12. The structure set forth in claim 11, wherein: said retainer means is releasable from said anti-extrusion members to facilitate the assembly and disassembly of said anti-extrusion members with respect to said plate. 